Orthopedic walking brace having a curved sole

ABSTRACT

Described herein are systems and devices for providing an orthopedic walking brace having a housing and a sole with a curved distal surface. The housing is configured to encompass and immobilize a patient&#39;s ankle against flexion. The distal surface of the sole has a posterior region, a mid region, and an anterior region. The posterior region is configured to lie under a heel portion of the patient&#39;s foot and has a first anterior-posterior (AP) curvature that increases from a posterior side of the posterior region toward a middle portion of the posterior region and decreases from the middle portion of the posterior region toward the mid region. The mid region is configured to lie under a center portion of the patient&#39;s foot. The anterior region is configured to lie under an anterior metatarsal and toe portion of the patient&#39;s foot and has a second AP curvature.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/295,440 filed Oct. 17, 2016; which claims priority to U.S.application Ser. No. 14/211,097 filed Mar. 14, 2014; which claimspriority to U.S. Provisional Patent Application No. 61/792,129, filed onMar. 15, 2013. Each of these applications are hereby incorporated byreference herein in their entireties.

BACKGROUND Field of the Disclosure

Orthopedic ankle casts and braces are designed to restrict anklemovement during recovery from injuries such as torn ligaments, sprainedankles, tibial stressed fractures and ankle fractures. An ankle cast istypically molded from rigid materials such as plaster or fiberglass. Itsupports the lower limb, holds the foot in a neutral position, andimmobilizes the ankle. Casts are often worn for several weeks or months,preferably without any weight on the joint to allow proper healing ofbroken bones and torn ligaments.

During further rehabilitation and strengthening of the ankle afterinitial stabilization of the injury, walking braces are used instead ofcasts to continue immobilization of the ankle while allowing gradualincrease in weight-bearing exercises such as walking. Some walkingbraces have a flat sole that is useful for standing, but difficult forwalking. Some walking braces have a rocker sole to create arolling-forward motion during stride, partially replacing lost functionsof the ankle joint. Nonetheless, other joints in the hip and the kneeoften need to compensate for lost ankle movements, making the use ofwalking braces fatiguing. In addition, walking braces are large andheavy, with stiff brace housings, and large soles to accommodate thesize of the housing. Some walking braces with a rocking bottom have athick sole, which can cause hip displacement when the thickness is notmatched on the patient's other foot. The added weight and height make itdifficult to use a walking brace, and the resulting unnatural gait canlead to further knee or hip discomfort.

Thus, there is a need for a walking brace that will allow the patient toapproximate a natural gait.

SUMMARY

Disclosed herein are systems and devices for providing walking braceshaving a sole with a curved distal surface. The sole thus provided has adistal surface with changing Anterior-Posterior (AP) curvatures andchanging Medial-Lateral (ML) curvatures to enable a natural gait whenwalking and to enhance stability when the patient is in a standingposition. Such curvature changes across the distal surface enable largeAP curvatures without large increases in the overall thickness of thesole.

According to one aspect, a sole is configured for use with an orthopedicwalking brace. The sole includes a proximal surface and a distalsurface. The proximal surface is configured to receive a patient's foot,and the distal surface has a posterior region, a mid region, and ananterior region. The posterior region is configured to lie under a heelportion of the patient's foot and has a first anterior-posterior (AP)curvature that increases from a posterior side of the posterior regiontoward a middle portion of the posterior region and decreases from themiddle portion of the posterior region toward the mid region. The midregion is configured to lie under a center portion of the patient'sfoot. The anterior region is configured to lie under an anteriormetatarsal and toe portion of the patient's foot and has a second APcurvature.

In some embodiments, the anterior region comprises greater than or equalto 30% of an AP length of the distal surface and less than or equal to40% of the AP length of the distal surface. In some embodiments, the midregion comprises greater than or equal to 35% of an AP length of thedistal surface and less than or equal to 45% of the AP length of thedistal surface. In some embodiments, the mid region is configured to liedirectly beneath the midfoot. In some embodiments, the first APcurvature has a maximum value greater than about 0.25 inch⁻¹. In someembodiments, a product of an AP length of the posterior region and amaximum value of the first AP curvature has a maximum value less thanabout 0.7. In some embodiments, the second AP curvature has a maximumvalue greater than about 0.1 inch⁻¹. In some embodiments, a product ofan AP length of the anterior region and a maximum value of the second APcurvature is greater than about 0.35. In some embodiments, the midregion is substantially flat. In some embodiments, the second APcurvature increases from a posterior side of the anterior region towarda middle portion of the anterior region and decreases from the middleportion of the anterior region toward an anterior side of the anteriorregion. In some embodiments, the distal surface has a firstmedial-lateral (ML) curvature that has a first peak adjacent to a medialedge, a second peak adjacent to a lateral edge of the distal surface andis substantially flat in between the first and the second peaks. In someembodiments, the distal surface is symmetric. In some embodiments, theproximal surface is rigid, and the distal surface is flexible. In someembodiments, the distal surface comprises a first material having afirst density and a second material having a second density that issmaller than the first density. In some embodiments, the first materialis rubber. In some embodiments, the second material is ethyl vinylacetate. In some embodiments, the proximal surface is formed of aplastic material. In some embodiments, a distance between a highestpoint on the distal surface and a ground surface defines a thickness anda maximum value of the thickness is about 0.75 inches.

According to another aspect, a method of immobilizing an ankle againstflexion while approximating a natural gait is provided. The methodincludes providing an orthopedic walking brace. The walking braceincludes a housing configured to encompass a patient's ankle. Thewalking brace includes a curved sole having a proximal surface and adistal surface, the proximal surface configured to receive the patient'sfoot, and the distal surface having a posterior region, a mid region,and an anterior region. The posterior region is configured to lie undera heel portion of the patient's foot and has a first anterior-posterior(AP) curvature that increases from a posterior side of the posteriorregion toward a middle portion of the posterior region and decreasesfrom the middle portion of the posterior region toward the mid region.The mid region is configured to lie under a center portion of thepatient's foot. The anterior region is configured to lie under ananterior metatarsal and toe portion of the patient's foot and has asecond AP curvature. The method includes encompassing the ankle of thepatient in the housing. The curved sole is configured to provide asubstantially smooth transition from heel-strike to mid-stance and frommid-stance to toe-off. In some embodiments, the curved sole provides arolling motion at an angular velocity that mimics a natural walking gaitcycle.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects and advantages will be appreciated morefully from the following description, with reference to the accompanyingdrawings. These depicted embodiments are to be understood asillustrative and not as limiting in any way.

FIG. 1 is a diagram showing the shank angle;

FIG. 2 is a plot showing illustrative measurements of shank angle andground reaction force when walking;

FIG. 3 illustrates the relationship between shank angle, curvature, andsole thickness;

FIG. 4 is a plot showing illustrative shank angular velocity during anormal walking gait cycle;

FIG. 5 is a side view of an illustrative walking brace having a curvedsole, in accordance with one embodiment;

FIG. 6 is a side view of an illustrative curved sole, in accordance withone embodiment, with a curvature plot for its distal surface;

FIG. 7 is a projection of the proximal surface of the illustrativecurved sole in FIG. 6, in accordance with one embodiment;

FIG. 8 is a projection of the distal surface of the illustrative curvedsole in FIG. 6, in accordance with one embodiment;

FIG. 9 is an anterior-posterior cross-sectional view of the illustrativecurved sole in FIG. 6, in accordance with one embodiment;

FIG. 10 is a medial-lateral cross-sectional view of the illustrativecurved sole in FIG. 6, in accordance with one embodiment; and

FIG. 11 is an exploded view of the curved sole in FIG. 6, showing anillustrative segmented and layered structure of the distal surface, withsegments formed by different materials, in accordance with oneembodiment.

DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS

To provide an overall understanding of the systems and devices describedherein, certain illustrative embodiments will now be described. For thepurpose of clarity and illustration, these systems and devices will bedescribed with respect to an orthopedic walking brace applied to apatient's lower leg and ankle. It will be understood by one of ordinaryskill in the art that the systems and devices described herein may beadapted and modified as appropriate. These systems and devices may beemployed in other suitable applications, such as for other types ofbraces that include a curved sole, and other such additions andmodifications will not depart from the scope hereof.

FIG. 1 shows the shank angle 120 and FIG. 2 provides a correspondingcurved line graph 220 of the shank angle 120 during the stance phase ofthe gait cycle. In FIG. 1, the lower limb of a person in a walkingposition is illustrated, with the anterior metatarsal and toe portion ofthe foot in contact with the ground. The shank angle 120 is measuredclockwise from the vertical axis 130 when at least a portion of thedistal surface of the foot is in contact with the ground. The shankangle 120 attains a value of 0 degrees if the shank and the thigh arealigned, as in an upright standing position; the shank angle 120 attainsa positive value when the knee is flexed to the back as shown in FIG. 1and attains a negative value when the lower leg is extended to the frontbeyond the upper thigh.

A gait cycle begins when a foot strikes the ground, and ends when thesame foot strikes the ground again. The motion of a lower limb in anormal walking gait cycle can be divided into two phases, a stance phaseduring which the foot is in contact with and supported by the ground,and a swing phase during which the lower limb is swung forward by thehip and knee. The stance phase begins when the heel of the foot 100strikes the ground, and ends when the toe 105 of the same foot leavesthe ground. The stance phase can be further divided into three stages:heel-strike, mid-stance, and toe-off. As the name implies, heel-strikeoccurs when the heel strikes the ground and rolls forward. Mid-stanceoccurs when the foot is flat on the ground, with the body center ofgravity directly above the foot. Toe-off follows mid-stance, and occurswhen the anterior metatarsal, or the ball of the foot, and the toes pushoff the ground to propel the body forward. During the stance phase, theankle and midtarsal joints provides dorsiflexion and plantar flexionmovements, while the anterior metatarsal and toe portion of the footprovides forward propulsion.

The shank angle 120, and the foot center of pressure 135 continuouslychange throughout the stance phase, with larger changes in the shankangle 120 during heel-strike and toe-off, as indicated by the curvedline graph 220 in FIG. 2. The horizontal axis 210 of this graphcorresponds to the time span of the stance phase in percentages, or thepercentage of the stance phase that has been completed. The primaryvertical axis 222 represents the shank angle 120 in degrees. Shadingsare used in FIG. 2 to approximate the three stages of the stance phase:regions 210, 212, and 214 correspond to heel-strike, mid-stance, andtoe-off, respectively. Although measurements of shank angles fordifferent individuals are expected to follow the same general pattern asthe line graph 220 through the stance phase, individual variations andstep-wise variations exist. The curved line graph 220 is presented as anillustrative example. Similar graphs can be drawn on an individual orother basis. As a person walks, the shank angle changes in a fashionsimilar to the curved line graph 220. Together, the ankle, tarsal, andmetatarsal joints support such movements with a rolling motion of thefoot while the foot is in contact with the ground. For a patient wearingan orthopedic walking brace, however, ankle movements are restricted. Asa result, either the patient takes smaller steps, or the knee and hipjoints compensate with additional flexion and extension. Both situationsresult in an unnatural gait that deviates significantly from the curvedline graph 220. Knee and hip discomforts also occur after prolongedperiods of use.

To help patients wearing a walking brace achieve a rolling motion of thefoot to better approximate a natural gait, soles for walking braces areoften designed to have a rocker bottom, or curved distal surface, tofacilitate changes in the shank angle as it would during natural gait.FIG. 3 illustrates the relationship between the shank angle and the APcurvature of the sole in an abstract fashion. Circular arcs 334 and 314correspond to the same Anterior-Posterior (AP) length 340 but differentcurvatures, where curvature is defined as the reciprocal of thecorresponding radii 336 and 338. In the case of non-circular arcs,curvatures change from point to point on the arc. The arcs 334 and 314represent side views of the anterior portions of curved soles, with thepoint 305 corresponding to where the anterior portion joins asubstantially flat mid portion. It is easy to see from FIG. 3 that asmall curvature (e.g., a large radius 338) in the AP direction providesa flatter sole, while a large AP curvature (e.g., a small radius 336)supports a larger change in shank angle and propels the user forward.Angles 310 and 320 in FIG. 3 represent the amount of change in shankangle required to approximate toe-off during natural gait. These twoangles are of the same value. The angle 320 corresponds to the arc 334.

Analogous to the arc 314, in many walking braces, the AP curvature atthe anterior end is too small to provide sufficient change in shankangle, causing the patient to take smaller and uneven steps. Analogousto the arc 334 where the corresponding height 332 is larger than theheight 330 of the arc 314, in many walking braces that do provide a moreideal curvature in the anterior portion or throughout the distal surfaceof the sole, the sole is substantially thicker, since the foot needs tolie on a flat surface when standing. A thicker sole leads to uneven leglengths and hip displacement if this thickness is not matched on thepatient's other foot. In yet some other walking braces where thicknessis controlled with smaller curvature but a given change in shank angleis still desired, the anterior portion of the sole has a longer APlength, analogous to extending the arc 314 towards the point 325 toapproach the angle 310. The AP length 344 of the arc between the point305 and the point 325, with the larger radius 338 and corresponding tothe angle 310, is much larger than the AP length 340 corresponding toarcs 334 and 314. A longer anterior portion pushes the mid portion ofthe sole towards the back, possibly affecting stability when a patientis in a standing position.

Unlike previous walking braces, in one aspect of the systems and devicesdescribed herein, the distal surface of the sole is designed accordingto the rate at which the shank angle changes throughout the stancephase. In other words, in addition to achieving a particular change inshank angle, some embodiments allow rolling motion of the walking braceto occur at an angular velocity that mimics a natural walking gaitcycle, as shown in FIG. 4. These embodiments are advantageous overprevious curved soles for walking braces because these embodimentsprovide sufficient acceleration in the anterior and posterior portionsof the sole to propel the user forward without incurring excessivethickness. These embodiments also allow the mid portion of the sole tospan over a longer length, and to lie beneath the center portion of thefoot for improved stability. In addition, with such designs where thedistal surface curves according to the rate at which the shank anglechanges throughout the stance phase, the mid portion of the sole has asmall but nonzero curvature, so that transitions from heel-strike tomid-stance and from mid-stance to toe-off are both gradual and smooth.Such small curvatures in the mid-portion of the sole do not causestability problems when a user is standing, in part because acombination of semi-rigid and flexible materials causes theweight-bearing mid portion to become essentially flat when the body massstays directly on top.

FIG. 4 provides a curved line graph 410 of typical shank angularvelocity during a normal walking gait cycle. The horizontal axis 430represents the span of the gait cycle using percentages, with regions434, 436 and 438 approximate the heel-strike, mid-stance, and toe-offstages of the stance phase, respectively. Regions 432 and 440 correspondto the swing phase during which changes in shank angle are facilitatedby hip and knee joints directly. The vertical axis 420 extends downwardand shows that the shank angular velocity varies between about 20 deg/sand about 180 deg/s. The curved line graph 410 shown in FIG. 4 isobtained by averaging angular velocity measurements from a plurality ofindividuals. In some embodiments of the walking brace where the sole iscustomized individually or customized for a particular group ofpatients, the desired angular velocity graph may differ from the curvedline plot 410, while still retaining a similar shape, with one valley inthe heel-strike stage, one hill in the mid-stance stage, and one valleyin the toe-off stage.

Returning to FIG. 2, also shown is a curved line graph 230 on thesecondary vertical axis 232, representing the ground reaction force 140(see FIG. 1), which is the force exerted by the ground on the footduring the stance phase of the gait cycle, when body weight passes overthe foot as the shank and the rest of body move forward. The horizontalaxis 210 represents the percentage of the stance phase that has beencompleted. At the beginning of heel-strike (approximately 0%) and theend of toe-off (approximately 100%), the reaction force is about 0Newton (N). Since in general, the amount of force going through the footis dependent on the patient's body weight, the curved line graph 230 ispresented as an illustrative example only. During heel-strike andtoe-off, the foot serves as a rigid lever to propel the body forward,causing the force 140 to be much larger than the patient's body weight.During mid-stance, the other foot is off the ground, and the patient'scenter of gravity is directly over the foot in the walking brace. Thus,the mid portion of the sole, corresponding to mid-stance, should besubstantially flat in the AP direction to provide stability, whether thepatient is walking or standing. In some embodiments, the mid portion ofthe sole is substantially flat, and configured to lie under a centerportion of the patient's foot, without comprising maximum curvatureachievable in the anterior or posterior end. In some embodiments, themid portion of the sole is configured to lie directly beneath themidfoot.

Furthermore, although not shown explicitly in a figure here, normallythe foot center of pressure flows through the foot continuously startingfrom the slightly lateral side of the heel towards the front in a medialdirection, exiting between the first and the second metatarsal andthrough the big toe. For walking braces with soles flat in theMedial-Lateral (ML) direction, any slight inversion or eversion of thelower leg results in the foot center of pressure jumping out to the edgeof the sole, a discrete event that interrupts a smooth gait. In oneaspect of the systems and devices described herein, the ML curvature islarge enough to accommodate a normal gait, and also small enough toallow stable standing. Such a feature is approximated by having, at eachML cross-section, an ML curvature that has a peak adjacent to the medialedge and another peak adjacent to the lateral edge of the distalsurface, while being substantially flat in between the two peaks. Tofurther mimic the progression of the foot center of pressure, MLcurvatures vary gradually from the posterior of the sole to theanterior, with larger peak values near the heel and smaller peak valuesat the mid portion.

FIG. 5 shows an embodiment of an orthopedic walking brace 500 with abrace housing 510 and a sole 520, which has a curved distal surface 522.The brace housing 510 can have any suitable form for providing supportto the lower leg and the foot. In this embodiment, the brace housing 510is a rigid shell that has a footbed portion 514, a heel portion 516, andan upright support portion 518. The footbed portion 514 has a planarsurface on the bottom for direct attachment to the sole 520, and mayenclose the patient's foot entirely or partially. The inside of thehousing 510 may be lined with cushioning material such as foam pads andinflatable components to provide comfort and to allow the user to adjustcompression level provided by the housing. In some embodiments, insteadof a rigid shell that immobilizes the ankle entirely, the housing can bemade of a semi-rigid material to allow small ankle movements during therecovery process.

FIG. 6 shows an illustrative embodiment 600 of a curve sole, withproximal surface 610 and distal surface 620. The distal surface 620 hasa curvature that approximates the angular velocity graph 410 plotted inFIG. 4. Starting from the most posterior point, the sole 600 can bedivided into three regions: a posterior region 630, a mid region 632,and an anterior region 634. The posterior region 630 extends from themost posterior point of the sole 600 to the mid region 632. The midregion 632 extends from the posterior region 630 to the anterior region634. The anterior region 634 extends from the mid region 632 to the mostanterior point of the sole 600. The AP length 625 of the sole 600 isdependent on the size of the orthopedic walking brace. For example, amedium-sized men's walking brace may have an AP length 625 of about 11inches. Walking braces designed for children are made proportionatelysmaller. The mid region 632 provides stability support to the patientwhen standing. The AP length 633 of the mid region 632 may be within therange of about 35% to about 45% of the AP length 625 of the sole 600,and in one example, is about 40% of the AP length 625 of the sole 600.The AP length 635 of the anterior region 634 may be within the range ofabout 30% to about 40% of the AP length 625 of the sole 600, and in oneexample, is about 35% of the AP length 625 of the sole 600. The length631 of the posterior region 630 can be derived if both the AP length 633of the mid region 632 and the AP length 635 of the anterior region 634are known. According to various examples, the AP length 631 of theposterior region 630 is within the range between about 15% to about 35%of the AP length 625 of the sole 600. In some embodiments, the AP length631 of the posterior region 630 is about 25% of the AP length 625 of thesole 600. The posterior region 630, the mid region 632, and the anteriorregion 632 correspond to the heel-strike, mid-stance, and toe-off stagesof the stance phase of the gait cycle, respectively.

As shown in FIG. 6, in some implementations, the toe-off anterior region634 has an AP curvature 644 that increases from a posterior side toreach a maximum value 648, then decreases towards the anterior side. Themaximum value 648 lies approximately within the middle portion of theanterior region 634. In some implementations, the maximum AP curvature648 is greater than about 0.10 inch⁻¹. For example, it may be about 0.11inch⁻¹.

When the size of a walking brace changes, the size of the sole changesas well. Shank angular velocity measurements for patients requiringwalking braces of different sizes may or may not differ from the curvedline graph 410 shown in FIG. 4, in part or entirely. Accordingly, whenthe AP length 625 of the sole 600 in FIG. 6 changes, the AP curvature ofthe distal surface 620 may be a scaled version of the AP curvatures 644,642, and 640 for the embodiment shown in FIG. 6. For example, the APcurvature 644 of the anterior region 634 may retain the same shape,range of values, and maximum value 648, when the AP length 635 of theanterior region 634 changes in proportion to the AP length 625 of thesole 600. Similar rules may apply to the curvature 642 of the mid region632 and the curvature 640 of the posterior region 630.

In some implementations, when the AP length 635 of the anterior region634 changes in proportion to the AP length 625 of the sole 600, the APcurvature 644 of the anterior region 634 also changes according to adesired scaled factor. For example, in FIG. 3, the ratio between the APlength 340 and the radius 336 is the sine function of the angle 320.Therefore, this ratio remains constant when the AP length 340 and theradius 336 change in value, as long as the angle 320 stays constant.Similarly, in some implementations of the sole 600 shown on FIG. 6, theratio between the AP length 635 of the anterior region 634 and theradius corresponding to the maximum curvature 648 of the anterior region634 stays approximately the same when the sole 600 changes in size. Insome implementations, the product of the maximum AP curvature 648 of theanterior region 634 and the AP length 635 of the anterior region 634 isgreater than about 0.35.

In some other implementations, the net forward velocity of the patient'sbody is assumed to follow approximately the same pattern and range ofvalues throughout the gait cycle among all people. The net forwardvelocity is also the tangential velocity at the sole, and the tangentialvelocity at the sole is the product of shank angular velocity and theradius of the curvature measured at the tangential point. Accordingly,when the sole 600 changes in size, the ratio of measured shank angularvelocities and corresponding curvature of the sole retains approximatelythe same pattern and range of values.

In some embodiments, the heel-strike posterior region 630 has an APcurvature 640 that increases from a posterior side of the posteriorregion 630 to reach a maximum value 646, then decreases towards the midregion 642. The maximum value 646 lies approximately within the middleportion of the posterior region 630. In some implementations, the APcurvature 640 of the posterior region 630 attains a value 650 muchlarger than zero at the most posterior point of the sole 600. Themaximum AP curvature 646 may be less than about 0.25 inch⁻¹. In oneexample, it is about 0.21 inch⁻¹. According to one implementation, theproduct of the maximum AP curvature 646 of the posterior region 630 andthe AP length 631 of the posterior region 630 is less than about 0.7.

As discussed above with respect to FIG. 2, the mid region 632 of thesole 600 is configured to lie under a center portion of the patient'sfoot, and may lie directly beneath the midfoot. Additionally, the midregion 632 is substantially flat. Thus, the mid region 632 has an APcurvature 642 that stays approximately constant over the region.According to one example, the mid region 632 has an AP curvature 642between about 0.024 inch⁻¹ and about 0.026 inch⁻¹. In some embodiments,the AP curvature 642 of the mid region 632 has a maximum value less thanabout 0.030 inch⁻¹. According to one implementation, the product of themaximum value of the AP curvature 642 of the mid region 632 and the APlength 633 of the mid region 632 is less than about 0.15.

FIG. 7 shows the projection of the proximal surface 610 of the curvedsole 600 in FIG. 6, according to one embodiment. The proximal surface610 is configured to receive the patient's foot and the footbed 514 (seeFIG. 5). According to various implementations, the sole 600 can beattached to the footbed 514 by adhesive, by interlocking mechanisms thatallow the sole 600 to be removed and changed if necessary, or by both anadhesive and an interlocking mechanism. As shown in the illustrativeembodiment in FIG. 7, the proximal surface 610 includes acircumferential rim 710, a circumferential groove 720, a raised platform750 with recessed volumes 760, positioned under the heel, and circularnotches 740, 742, 744, and 746. The circumferential rim 710, thecircumferential groove 720, the raised platform 750, and the circularnotches 740, 742, 744 and 746, on the proximal surface 610, can becoupled to corresponding structures (not shown) on the bottom of thefootbed 514 to allow precise and secure attachment of the sole 600 tothe footbed 514, which is part of the upper housing 510. The upperhousing 510 supports the ankle and the lower leg. The AP length 625 ofthe sole 600 is dependent on the size of the upper housing 510. In otherembodiments, the proximal surface 610 includes different structures forsecuring the sole 600 to the footbed 514. For example, the proximalsurface 610 may include protrusions that couple with indents in thefootbed 514.

In FIG. 7, the proximal surface 610 is symmetrical around thelongitudinal axis. In one implementation, the distal surface 620 of thesole 600 shown in FIG. 6 is also symmetrical, allowing the sole 600 tobe used for either a left or a right foot. In other implementations, theproximal surface 610 is designed with asymmetric structures. Forexample, instead of having a notch 742 as a mirror image of the notch746, and a notch 740 as a mirror image of the notch 744, in someembodiments, notches on the proximal surface 610 may be located atasymmetric positions around the longitudinal axis. In other examples,the proximal surface 610 may include more than four notches or less thanfour notches. Furthermore, in other embodiments, the proximal surface610 is constructed asymmetrically, shaped conform to the shape of apatient's foot, or with raised portions to compensate for a patient'swalking gait characteristics, such as pronation.

FIG. 8 is a projection of the distal surface 620 of the illustrativecurved sole 600, according to one embodiment. The anterior-posterioraxis 810 divides the sole 600 into two halves, and passes through theposterior point of the sole 600. In some embodiments, the two halves areidentical, i.e., the distal surface is symmetric. The distal surface mayalso be asymmetric. For example, the distal surface 620 may be designedto include arch support, and/or to accommodate pronation of a left or aright foot. The width 830 of the sole 600 is measured across the widestmedial-lateral cross-section of the sole 600. In this embodiment, thewidth 830 is about 45% of the full AP length 625 (see FIG. 6) of thesole 600. When a walking brace is customized according to injury type oruser preferences, the ratio between the width 830 of the sole 600 andthe full AP length 625 of the sole 600 may be in the range between about35% to about 55%.

FIG. 9 is an anterior-posterior cross-sectional view of the curved sole600, according to one embodiment. The cross-section is taken at theanterior-posterior axis 810 shown in FIG. 8. The raised platform 750 hasa length 910 and a height 915. According to one example, the length 910is about 2.6 inches and the height 915 is about 0.25 inches. The raisedplatform 750 is spaced apart from the circumferential rim 710 by adistance 920. In one example, the distance 920 is about 0.5 inches. Therim 710 has a rim height 925 of about 0.4 inches. The rim height 925 ofthe rim 710 may vary along the edge of the distal surface 620. Thethickness 940 of the sole 600 is approximately the same as the distancebetween the highest point on the distal surface 620 and the groundlevel. In some embodiments, the thickness 940 of the sole 600 is about0.75 inches. The thickness 940 of the sole 600 may vary depending on thesize of the sole 600.

FIG. 10 is a medial-lateral cross-sectional view of the curved sole 600,wherein the cross-section is made at the medial-lateral line 820 of FIG.8, perpendicular to the anterior-posterior axis 810. The circumferentialgroove 720 has a width 1010 and a depth 1020 at the medial-lateral line820. According to one example, the width 1010 is about 0.25 inches andthe depth 1020 is about 0.15 inches. As shown in FIG. 10, themedial-lateral width 1030 of the raised platform 750 is about 3.0 inchesat the medial-lateral line 820.

FIG. 11 is an exploded view of the distal surface 620 of the curved sole600 shown in FIG. 6. In practice, the sole 600 can be manufactured usingvarious materials and various processes. In one implementation, the sole600 is manufactured from a mold using one type of material, for example,vulcanized natural rubber, which is preferred for its anti-slip andshock-absorbing properties. Natural rubber has a high density, and thusadds significant weight to the walking brace. To reduce the overallweight of the sole 600 yet providing shock absorbance and wearresistance, in some implementations, the sole 600 is made by fusing anoutsole layer and a midsole layer into a single piece, where the outsolelayer corresponds to the distal surface 620 of the sole 600, and themidsole layer corresponds to the proximal surface 610 of the sole 600.The distal surface 620 and the proximal surface 610 can be made ofmaterials with different densities and rigidities.

In some implementations, the distal surface 620 is made of two differenttypes of materials in a segmented and layered structure. As shown inFIG. 11, thin layers of inserts 1120, 1130, and 1140 are made of naturalrubber, while the main body 1110 is made of a lighter material such as100% EVA (Ethyl-Vinyl Acetate), known for its durability andshock-absorbency. The first insert 1120 is placed at around theposterior region of the distal surface 620 to reduce skid duringheal-strike, while the second insert 1130 and the third insert 1140 areplaced below the anterior region and part of the mid region to minimizeslippage during mid-stance and toe-off. The first insert 1120 has ahorseshoe shape, which reduces its overall surface area and its weight,without comprising anti-slip and shock-absorbing properties. The secondinsert 1130 is also shaped like a horse-shoe, with a central hollowportion configured to fit the third insert 1140. The third insert 1140is shaped like an isosceles trapezoid in this example. All of the threeinserts 1120, 1130, and 1140 include patterned grooves. Different shapesfor the inserts and different patterns for the grooves can be used inother embodiments. According to various examples, the inserts 1120, 1130and 1140 may have different colors, possibly matching the colors ofother parts of the walking brace. In some configurations, more than, orless than three inserts are included in the distal surface 620. Forexample, instead of the second insert 1130 and the third insert 1140, asingle large insert (not shown) may be placed below the anterior regionand part of the mid region of the distal surface 620.

It is to be understood that the foregoing is merely illustrative, and isnot to be limited to the details given herein. While several embodimentshave been provided by the present disclosure, it should be understoodthat the disclosed systems and devices and their components may beembodied in any other specific forms without departing from the scope ofthe disclosure.

Variations and modifications will occur to those of skill in the artafter reviewing this disclosure, where disclosed features may beimplemented in any combination and subcombinations (including multipledependent combinations and subcombinations), with one or more otherfeatures described herein. The various features described or illustratedabove, including any components thereof, may be combined or integratedin other devices, systems, or methods; moreover, certain features may beomitted or not implemented.

Examples of changes, substitutions and alternations are ascertainable byone skilled in the art and to be made without departing from the scopeof the information disclosed herein. All references cited herein areincorporated by reference in their entirety and made part of thisapplication.

What is claimed is:
 1. A sole configured for use with an orthopedicwalking brace, comprising: a proximal surface and a distal surface, theproximal surface configured to receive a patient's foot, and the distalsurface having a posterior region, a mid region, and an anterior region,wherein: the posterior region is configured to lie under a heel portionof the patient's foot and has a first anterior-posterior (AP) curvaturethat increases from a posterior side of the posterior region toward amiddle portion of the posterior region and decreases from the middleportion of the posterior region toward the mid region, the mid region isconfigured to lie under a center portion of the patient's foot, and theanterior region is configured to lie under an anterior metatarsal andtoe portion of the patient's foot and has a second AP curvature.
 2. Thesole of claim 1, wherein the anterior region comprises greater than orequal to 30% of an AP length of the distal surface and less than orequal to 40% of the AP length of the distal surface.
 3. The sole ofclaim 1, wherein the mid region comprises greater than or equal to 35%of an AP length of the distal surface and less than or equal to 45% ofthe AP length of the distal surface.
 4. The sole of claim 1, wherein themid region is configured to lie directly beneath the midfoot.
 5. Thesole of claim 1, wherein the first AP curvature has a maximum valuegreater than about 0.25 inch⁻¹.
 6. The sole of claim 1, wherein aproduct of an AP length of the posterior region and a maximum value ofthe first AP curvature has a maximum value less than about 0.7.
 7. Thesole of claim 1, wherein the second AP curvature has a maximum valuegreater than about 0.1 inch⁻¹.
 8. The sole of claim 1, wherein a productof an AP length of the anterior region and a maximum value of the secondAP curvature is greater than about 0.35.
 9. The sole of claim 1, whereinthe mid region is substantially flat.
 10. The sole of claim 1, whereinthe second AP curvature increases from a posterior side of the anteriorregion toward a middle portion of the anterior region and decreases fromthe middle portion of the anterior region toward an anterior side of theanterior region.
 11. The sole of claim 1, wherein the distal surface hasa first medial-lateral (ML) curvature that has a first peak adjacent toa medial edge, a second peak adjacent to a lateral edge of the distalsurface, and is substantially flat in between the first and the secondpeaks.
 12. The sole of claim 1, wherein the distal surface is symmetric.13. The sole of claim 1, wherein the proximal surface is rigid, and thedistal surface is flexible.
 14. The sole of claim 1, wherein the distalsurface comprises a first material having a first density and a secondmaterial having a second density that is smaller than the first density.15. The sole of claim 14, wherein the first material is rubber.
 16. Thesole of claim 14, wherein the second material is ethyl vinyl acetate.17. The sole of claim 1, wherein the proximal surface is formed of aplastic material.
 18. The sole of claim 1, wherein a distance between ahighest point on the distal surface and a ground surface defines athickness and a maximum value of the thickness is about 0.75 inches. 19.A method of immobilizing an ankle against flexion while approximating anatural gait, comprising: providing an orthopedic walking brace,comprising: a housing configured to encompass a patient's ankle; and acurved sole having a proximal surface and a distal surface, the proximalsurface configured to receive the patient's foot, and the distal surfacehaving a posterior region, a mid region, and an anterior region,wherein: the posterior region is configured to lie under a heel portionof the patient's foot, and has a first anterior-posterior (AP) curvaturethat increases from a posterior side of the posterior region toward amiddle portion of the posterior region and decreases from the middleportion of the posterior region toward the mid region, the mid region isconfigured to lie under a center portion of the patient's foot, and theanterior region is configured to lie under an anterior metatarsal andtoe portion of the patient's foot and has a second AP curvature; andencompassing the ankle of the patient in the housing, wherein the curvedsole is configured to provide a substantially smooth transition fromheel-strike to mid-stance and from mid-stance to toe-off.
 20. The methodof claim 19, wherein the curved sole provides a rolling motion at anangular velocity that mimics a natural walking gait cycle.